I belong to a number of Yahoo listrs, several of which prohibit top posting. eM Client seems to not know any other format for replies. Is there a way to bottom post or interleave a reply with the original? At the moment, I can't even remove the bar on the left side.

1) when creating a template, you can set font and preferred text color (under the template name), but when the format of message (that you are replying to) is specified explicitly, it can be changed only manually.
2) This is not implemented yet. We are sorry for this inconvenience.